Influence of combined antecedent and main rainfall temporal patterns on landslides

Abstract Rainfall-induced slope failures present significant global risks, resulting in substantial economic losses and threatening lives. As climate change potentially impacts the frequency and intensity of extreme rainfall events, which may influence the likelihood of rainfall-induced slope failures, a deeper understanding of these failures can be beneficial. While the effects of rainfall infiltration—particularly concerning factors like critical intensity, duration, pattern, and antecedent conditions—on slope stability have been studied, research has typically focused on either antecedent rainfall or main rainfall. This has potentially led to an oversight of the possible combined effects of these rainfall patterns. This study aims to evaluate the influence of the combined temporal pattern of antecedent and main rainfall. Four typical rainfall patterns of advanced, normal, delayed, and uniform rainfall are designed based on historical records from Hong Kong are evaluated in this study. Our findings indicate that these combined rainfall patterns influence slope stability, time to reach minimum safety factor, and rate of safety factor reduction. Notably, the combination of antecedent rainfall with delayed and uniform main rainfall patterns creates the most critical conditions, agreeing with historical rainfall records associated with past notable landslides in Hong Kong. Additionally, various definitions of antecedent rainfall—whether immediately before main rainfall or separated by a gap—along with their critical durations, are often adopted in previous studies. This study explores these influences, particularly in the context of combined rainfall patterns, revealing that the combination of delayed antecedent rainfall and advanced main rainfall is particularly sensitive to the gap durations. The practical implications of our findings are also discussed. (260 words)